Shaft seal

ABSTRACT

A shaft seal for a rotatable shaft which is surrounded by a substantially rigid structural element, has a ring-shaped body portion adapted to be supported by the structural element and having an axis and two axially spaced end faces, a radially displaceable ring-shaped inner portion located radially inwardly of the body portion, extending in an axial direction, and together with the body portion forming an axially extending gap, at least one sealing lip provided in the inner portion and subjected to radial vibrations during rotation of the shaft which vibrations are transmitted to the radially displaceable inner portion and displace the latter, and elements for damping radial vibrations of the sealing lip.

BACKGROUND OF THE INVENTION

The present invention relates to a shaft seal. More particularly, itrelates to a shaft seal for a rotatable shaft surrounded by asubstantially rigid structural element.

Shaft seals have been proposed in the art, wherein when the shaftrotates with a great number of revolutions or the shaft drily rotate insealing lips, so-called "stick-slip" effect takes place, as a result ofwhich effect the sealing lips are radially displaced under the action ofradial vibrations. These vibrations are connected with an unpleasantwhistling sound, and in certain cases can progressively increase so thatthe sealing lips or the shaft seal will be destroyed when inherentdamping capability of an element which urges the sealing lips toward theshaft cannot longer limit the above-mentioned vibrations.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a shaftseal which avoids the disadvantages of the prior art.

More particularly, it is an object of the present invention to provide ashaft seal whose vibrations are limited to a permissible magnitude oreliminated at all.

In keeping with these objects, and with others which will becomeapparent hereinafter, one feature of the present invention, brieflystated, resides in a shaft seal for a rotatable shaft including aringshaped body portion and a radially displaceable ringshaped innerportion located radially inwardly of the body portion and together withthe latter forming a gap, wherein means for damping radial vibrations ofsealing lips arranged at the inner portion is provided. When theabove-mentioned damping means is provided in the shaft seal, vibrationsof the sealing lip generated during rotation of the shaft andtransmitted to the radially displaceable inner portion of the shaft sealare limited so that they are retained within permissible limits oreliminated at all.

Another feature of the present invention is that the gap between thebody portion and the inner portion has a width which is smaller than adistance by which the inner portion is displaced under the action of thevibrations of the sealing lip. When the gap is so dimensioned, an innersection of the body portion located adjacent to and facing toward theinner portion of the shaft seal, forms the above-mentioned dampingmeans.

Still another feature of the present invention is that the body portionmay be formed as a separate member connected with the inner portion. Inthis case, the separate member serves as the damping means. The separatemember may be constituted by a synthetic plastic material.

An additional feature of the present invention is that the damping meansmay include a damping element which is located in the gap between thebody portion and the inner portion. The damping element may beconstituted by an elastomeric material.

A still additional feature of the present invention is that the dampingmeans may be formed by a stationary element abutting against the face ofthe sealing lip which is axially spaced from the region wherein the bodyportion is connected with the inner portion of the shaft seal.

A further feature of the present invention is that the stationaryelement may be located between a shoulder of a structural elementsurrounding the shaft and respective faces of the body portion and thesealing lip.

Finally, a still further feature of the present invention is that anadditional sheet of an absorbent material may be located between thestationary element and the respective faces of the body portion and thesealing lip, which absorbent material may be impregnated by a viscouslubricant. It is also possible that the above-mentioned damping elementlocated in the gap between the body portion and the inner portion may beconstituted by an absorbent material which is impregnated by a viscouslubricant.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a section of a portion of a shaft seal inaccordance with the present invention wherein damping means is formed byan outer ring-shaped body portion of the seal;

FIG. 2 is a view showing a section of a portion of a shaft seal inaccordance with another embodiment of the present invention;

FIG. 3 is a view showing a section of a portion of a shaft seal inaccordance with a further embodiment of the present invention, whereindamping means is formed by a damping element located in a gap betweenthe outer ring-shaped body portion and an inner portion of the shaftseal;

FIG. 4 is a view showing a section of a portion of a shaft seal inaccordance with a still further embodiment of the present invention,wherein damping means is formed by a friction disc abutting againstfaces of the outer ring-shaped body portion and of sealing lip providedin the inner ring-shaped portion;

FIG. 5 is a view showing a section of a portion of a shaft seal inaccordance with an additional embodiment of the present inventionwherein damping means is formed by an element of an absorbent materiallocated in a gap between the outer ring-shaped body portion and theinner ring-shaped body portion of the shaft seal; and

FIG. 6 is a view showing a section of a portion of a shaft seal inaccordance with a still additional embodiment of the present invention,wherein damping means is formed by a friction disc abutting against aface of the outer ring-shaped body portion, and wherein an additionalsheet of an absorbent material is located between the friction disc anda face of the sealing lip of the shaft seal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A shaft seal 10 shown in FIG. 1 has a ring-shaped body portion 12 whichis reinforced by a metal ring 14. The ring-shaped body portion 2 has twoaxially spaced ends faces 16 and 18. A ring-shaped inner portion 20 islocated radially inwardly of the body portion 12 and connected with thelatter in the region adjacent to the end face 16. The inner portion 20extends in the direction from the end face 16 toward the end face 18 ofthe body portion 12 over an axial distance corresponding to at least apart of the axial length of the body portion 12. The inner portion 20 isradially displaceable relative to the body portion 12.

A sealing lip 22 is provided in the inner portion 20 and has a sealingedge 24 facing toward a shaft to be sealed. In operation the sealingedge 24 of the sealing lip 22 abuts against the shaft. The sealing lip22 is located closer to the end face 18 of the body portion 12 than aregion wherein the inner portion 20 is connected with the body portion12. An annular gap 26 is formed between the body portion 12 and theinner portion 20 or the lips 22, which annular gap extends in the axialdirection and is open at the face 18 of the body portion 12. The sealinglip 22 has a groove provided in a surface facing toward the body portion12, in which groove an element is located operative for urging thesealing edge 24 of the sealing lip 22 toward the shaft. A worm spring 28can be utilized as such urging element. The inner gap 26 has a radialwidth 30 which corresponds to maximum magnitude of permissiblevibrations of the sealing lip 22. In this case surfaces of the wormspring 28 or the sealing lip 22 facing toward the body portion 12 abutagainst a surface of the body portion 12 facing toward the innerportion, so that the vibrations of the sealing lip 22 and the innerportion 20 are limited by a section of the body portion 12 adjacent tothe gap 26. Since the vibrations cannot exceed a predeterminedmagnitude, the above-mentioned destruction of the sealing lip isprevented.

FIG. 2 shows a shaft seal in accordance with another embodiment of thepresent invention. In this shaft seal a body portion is formed by ametal ring 40 having an angular cross-section. A separate ring-shapedelement 52 is located radially inwardly of the ring 40. An inner portion44 having a transition region 46 is connected to a radial leg 42 of thering 40. The inner portion 44 is provided with a sealing lip 48 whichhas the sealing edge 24. The locations of the sealing lip 48 and thetransition region 46 relative to the end faces 16 and 18 of the ring 40are similar to those of the shaft seal shown in FIG. 1. The urgingelement 28 is also located in a groove provided in the sealing lip 48.

The separate ring-shaped element 52 which is located between an axialleg 50 of the ring 40, together with the inner portion 44 forms theannular gap 26. A width of the annular gap 26 is so selected that theseparate ring-shaped member 52 serves as damping means for damping theradial vibrations of the sealing lip 48 and the inner portion 44. Thering 52 is constituted by a deformable material which possesses highdamping characteristics, such as an elastomeric material. In certaincases it can be advantageous with the ring-shaped member 52 isconstituted by a relatively hard undeformable material.

In accordance with the embodiment shown in FIG. 3, the shaft seal 10 isarranged in a structural element 60 surrounding the shaft to be sealed.The end face 18 of the shaft seal 10 abuts against a shoulder 62 of thestructural element 60. As can be seen from FIG. 3, an annular gap 64which is formed between the body portion 12 and the radiallydisplaceable inner portion 12 have a width 66 which exceeds the width 30of the gap 26 of the shaft seal shown in FIGS. 1 and 2. A filling insert68 of a damping material, such as an elastomeric material, is insertedinto the thus-enlarged annular gap 64.

The shaft seal in accordance with the embodiment shown in FIG. 5substantially corresponds to that shown in FIG. 3. However, a fillinginsert 70 located in the annular gap 64 of the shaft seal shown in FIG.5 is constituted by an absorbent material, preferably felt. The fillinginsert 70 is impregnated by a lubricant which issues from the fillinginsert when the sealing lip 22 vibrates. The lubricant flows over anouter side of the sealing lip up to the sealing edge 24 of the latter,so that this lubricant breaks off the vibrations.

In the shaft seal in accordance with the embodiment shown in FIG. 4 aring-shaped disc 80 is provided, which is located between the shoulder62 of the structural element 60 and the end face 15 of the body portionof the shaft seal. A radially outer portion of the disc 80 abuts againstthe end face 18 of the body portion, whereas a radially inner portion ofthe disc 80 abuts against the sealing lip 22. The disc 80 is preferablyconstituted by metal and has a rough surface abutting against thesealing lip 22, so that the vibrations of the sealing lip are dampedunder the action of friction between the disc and the sealing lip. Theannular gap between the body portion, the sealing lip 22 or the innerportion, and the disc 80 remains, in this embodiment, empty.

The shaft seal in accordance with the embodiment shown in FIG. 6 is, tosome extent, similar to the above-mentioned embodiment. However, in theshaft seal shown in this Figure, the ring-shaped disc 80 is locatedbetween the shoulder 62 of the structural element 6 and a ball bearing82 of the shaft. The ball bearing 82 is located between the structuralelement 60 and a shaft 84. Thus, the disc 80 is held between a face ofthe ball bearing which faces toward the structural element, and the endface 18 of the body portion 12.

A sheet 86 of an absorbent material which can be constituted by feltsimilarly to that shown in FIG. 5, is located between the disc 8 and aface of the sealing lip 22 which faces toward the latter. An innersurface of the sheet 86 abuts against an outer surface of the shaft 84.The sheet 86 is also impregnated by a lubricant and contacts the shaftat a location which is close to the sealing edge 24 of the sealing lip22. Therefore, the region of the shaft which cooperates with the sealingedge 24 is so lubricated that the above-mentioned "stick-slip" effectcannot take place in this case. In the shaft seal in accordance withthis embodiment of the invention it is possible to utilize the annulargap 26 as a reservoir of lubricant.

In the shaft seals shown in FIGS. 1-4 the vibrations are maintainedwithin permissible limits. The shaft seals in accordance with theembodiments shown in FIGS. 5 and 6 directly counteract "stick-slip"effect by means of the absorbent element which is impregnated bylubricant. In the shaft seal in accordance with the embodiment shown inFIG. 6, this is performed continuously, whereas in the shaft seal inaccordance with the embodiment shown in FIG. 5, lubrication is performedonly when the vibrations occur inasmuch as when the sealing lip vibratesthe filling insert 70 is squeezed so that the lubricant issues from thelatter and flows to the sealing edge 24.

In the known shaft seals inherent characteristics of the shaft sealswere not sufficient to maintain the vibrations within permissiblelimits. In accordance with the present invention, additional dampingmeans is provided, for damping the vibrations of the sealing lip. Inaccordance with the present invention, the damping means is formed by acorresponding dimensioning of the annular gap 26, by the provision ofthe damping material 68 in the annular gap 64, by the provision of thering-shaped disc 80 cooperating with the sealing lip 22, or by theprovision of reservoirs of lubricant.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in ashaft seal, it is not intended to be limited to the details shown, sincevarious modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:
 1. A shaft seal for a rotatable shaftwhich is surrounded by a substantially rigid structural element,comprising a ring-shaped body portion adapted to be supported by thestructural element and having an axis, two axially spaced end faces, andan inner surface facing toward the shaft; a radially displaceablering-shaped inner portion located radially inwardly of said body portionand having an outer surface facing toward said inner surface of saidbody portion and together with the same forming an axially extendinggap, said inner portion being connected with said body portion adjacentone axial end of said gap, said inner portion carrying at least onesealing lip which is urged toward the shaft so as to sealingly abutagainst the latter and which is subjected to radial vibrations duringrotation of the shaft, which vibrations are transmitted to said radiallydisplaceable inner portion and displace the latter; means for urgingsaid one sealing lip toward the shaft; and means for damping radialvibrations of said sealing lip said damping means being separate fromsaid urging means.
 2. The shaft seal as defined in claim 1, wherein saidurging means includes at least one urging element arranged to urge saidinner portion toward said shaft.
 3. The shaft seal as defined in claim1, wherein said lip has an edge facing toward the shaft and sealinglyabutting against the latter, when said inner portion is urged towardsaid shaft.
 4. The shaft seal as defined in claim 1, wherein one of saidend faces of said body portion is located at the side of said one axialend of said gap, whereas the other end face is located at the axiallyopposite side, said inner portion being connected with said body portionby a transition section, said sealing lip being spaced from said otherend face of said body portion by a distance which is smaller than thedistance by which said transition section is spaced from said other endface.
 5. The shaft seal as defined in claim 1, wherein said gap is openin the region of its other axial end.
 6. The shaft seal as defined inclaim 1, wherein one of said end faces of said body portion is locatedat the side of said one axial end of said gap, whereas the other endface is located at the axially opposite side, said body portion havingan axial length, said inner portion extending toward said other face ofsaid body portion by a distance corresponding to at least a part of saidaxial length of said body portion.
 7. The shaft seal as defined in claim1, wherein said damping means is associated with said radiallydeformable inner portion.
 8. The shaft seal as defined in claim 1,wherein said damping means is associated with said lip of said innerportion.
 9. The shaft seal as defined in claim 1, wherein said gap is anannular gap.
 10. The shaft seal as defined in claim 1, wherein said bodyportion is reinforced; and further comprising an element reinforcingsaid body portion.
 11. The shaft seal as defined in claim 1, whereinsaid body portion has an inner section forming said inner surfacethereof, said inner portion being radially outwardly displaceable by apredetermined distance under the action of the vibrations of the sealinglip, said gap between said body portion and said inner portion having awidth which is smaller than the distance by which said inner portion isradially outwardly displaced under the action of the vibrations of saidsealing lip so that said inner section of said body portion forms saiddamping means.
 12. The shaft seal as defined in claim 1, wherein saidbody portion is a separate member connected with said inner portion. 13.The shaft seal as defined in claim 12, wherein said separate member isconstituted by a synthetic plastic material.
 14. The shaft seal asdefined in claim 2, wherein said damping means includes a dampingelement located in said gap between said body portion and said innerportion.
 15. The shaft seal as defined in claim 14, wherein said dampingelement is constituted by an elastomeric material.
 16. The shaft seal asdefined in claim 1, wherein one of said end faces of said body portionis located at the side of said one axial end of said gap, whereas theother end face is located at the axially opposite side, said sealing liphaving a face adjacent to said other face of said inner portion, saiddamping means being formed by a stationary element abutting against saidface of said sealing lip.
 17. The shaft seal as defined in claim 16,wherein the structural element surrounding the shaft has a shoulder,said stationary element being located between the shoulder of thestructural element, on the one hand, and said other face of said bodyportion and said face of said sealing lip, on the other hand.
 18. Theshaft seal as defined in claim 17; and further comprising a sheet of anabsorbent material located between said stationary element, on the onehand, and said other face of said body portion and said face of saidinner portion, on the other hand, said sheet extending through said gapup to the shaft.
 19. The shaft seal as defined in claim 18, wherein saidsheet is constituted by felt.
 20. The shaft seal as defined in claim 18,wherein said sheet of an absorbent material is impregnated by a viscouslubricant.
 21. The shaft seal as defined in claim 1, wherein saiddamping means includes an element of an absorbent material located insaid gap between said body portion and said inner portion.
 22. The shaftseal as defined in claim 21, wherein said element of an absorbentmaterial is impregnated by a viscous lubricant.
 23. The shaft seal asdefined in claim 2, wherein said urging element is arranged in saidinner portion.